Chemical Composition and Explosivity of Volcanoes

Chemical Composition and explosivity of volcanoes

Earth Science: Unit 3- Plate Tectonics and Volcanoes

Goal:

Part One

1. Students will make and test out a hypothesis on how the viscosity of a liquid affects the ease with which bubbles can be blown into the liquid.
2. Students will determine that the higher the viscosity of the liquid, the more force it requires to move gas through the liquid.
3. E3.4d: Explain how the chemical composition of magmas relates to platetectonics and affects the geometry, structure, and explosivity of volcanoes.

Part Two

1. Students will make and test out a hypothesis on how viscosity of a liquid affects the pressure of gas bubbles that form in and are subsequently released from the liquid when the liquid is heated to boiling point.
2. Students will determine that liquids with a higher viscosity will have a more explosive release of gas bubbles that form when the liquid is at the boiling point.
3. E3.4d: Explain how the chemical composition of magmas relates to plate tectonics and affects the geometry, structure, and explosivity of volcanoes.

Background

Magma that has higher silica content has a higher viscosity. A volcano that contains this type of magma will have a more explosive eruption.

Vocabulary

Chemical composition

Explosivity

Magma

Silica

Time frame:

15 minutes for part one, 15 minutes for part two.

Materials

Part one-

Test tubes (3 per group)

Corn syrup

Water

Graduated cylinders

Straws

Goggles

Part two-

Cooked oatmeal- the amount needed depends on whether or not this part is being done as ademonstration or as a student lab

300 ml beakers- 2 per group

Hot plates

Goggles

Procedure

Part One- Viscosity and the ease of bubble(gas) movement

1.Prepare three different mixtures of water and syrup. Make one mixture with pure syrup, one mixture with a small amount of water and one mixture with a larger amount of water. Each group will need about 15 ml of each liquid. (teacher can prepare before hand or have students make their own)

2.Determine which syrup has the highest and which syrup has the lowest viscosity.

3.Make a hypothesis about the amount of force required to blow a few bubbles in each of the syrup mixtures.

4.Pour 15 ml of each of the liquids into 3 different test tubes.

5.Place a straw in the mixture and gently blow a few bubbles through the liquid. Cover the top of the test tube with a paper towel so the liquid does not spatter into your face.

6.Repeat with the other 2 liquids.

7.Rank the mixtures in order of easy to hard to blow bubbles in the liquid.

Part Two- Explosivity of Bubbles and Viscosity

This can be done as a teacher demonstration or as a lab for students to conduct

1. Measure and place 200 ml of water into a beaker.
2. Measure and place 200 ml of cooked oatmeal in another beaker.
3. Place both beakers on a hot plate and bring to boil
4. While the materials are heating up make a hypothesis about which material will have the most explosive bubble erupt when the material starts to boil.
5. Observe the materials as they start to boil. Write down your observations.
6. Dispose of the materials according to your teachers directions.

Options for more inquiry

After writing a hypothesis, students could design experiments for part one and part two.

Expected results

Part one- Students should see that it is easier to blow bubbles in the liquid that has a lower viscosity- not as much energy is required.

Part two- Student should see that the oatmeal (with the higher viscosity) produced more explosive bubble of gas.

Chemical Composition and Explosivity of Volcanoes

Student Master

Name ______

Part One- Viscosity and the ease of bubble (gas) movement

1.Prepare three different mixtures of water and syrup. Make one mixture with pure syrup, one mixture with a small amount of water and one mixture with a larger amount of water. You will need 15 ml of each liquid.

2.Determine which syrup mixture has the highest viscosity and which syrup mixture has the lowest viscosity.

3.Make a hypothesis about the amount of force required to blow a few bubbles in each of the syrup mixtures. Record your hypothesis in this space: Provide a rationale for your hypothesis.

4.Pour 15 ml of each of the liquids into 3 different test tubes.

5.Place a straw in the mixture and gently blow a few bubbles through the liquid. Cover the top of the test tube with a paper towel so the liquid does not spatter into your face.

6.Repeat with the other 2 liquids.

7.Use the space below to rank the mixtures in order of easy to hard to blow bubbles through the liquid.

8.Make a conclusion about how viscosity affects how hard it for bubbles to flow through the liquid.

9.Would magma with a high viscosity allow gas bubbles to move through it easily?

10.Would magma with low silica content allow gas bubbles to move through it easily? Explain your answer.

Part Two- Explosivity of Bubbles and Viscosity

1. Measure and place 200 ml of water into a beaker.

1. Measure and place 200 ml of cooked oatmeal in another beaker.

1. Place both beakers on a hot plate and bring to a gentle boil

1. While the materials are heating up make a hypothesis about which material will have the most explosive bubble erupt when the material starts to boil. Record you hypothesis here: Provide a rationale for your hypothesis.

1. Observe the materials as they start to boil. Write down your observations.

1. Make a conclusion about how viscosity of a liquid affect the explosiveness of the gas bubbles that for in the liquid when heated to boiling.

1. Dispose of the materials according to your teachers directions.

1. Describe the eruptions of a volcano that has magma that has a high viscosity.

1. What type of eruptions would you expect a volcano with magma that contains a low viscosity to have? Explain why.